Battery cells, for example lithium-ion battery cells, can be found, for example, in battery systems of motor vehicles, for example electric motor vehicles or hybrid motor vehicles in conjunction with drives of the motor vehicles.
Battery systems for use in the drive train of motor vehicles are also referred to as traction batteries. Such battery systems can be embodied as systems composed of battery cells and battery management system. In order to provide the power output which is required in hybrid vehicles and electric vehicles, battery cells, the elementary voltage sources, are connected in series and partially also in parallel. In the case of electric vehicles, battery systems have in some cases voltages above 450 V, and even in the case of hybrid vehicles the voltage of 60 V, which is assumed as a safety threshold for contact with people, is exceeded. If such battery systems are short-circuited as a result of external events, such as accidents or a malfunction in the actuation of a power switch, currents, with current strengths which may cause the battery to burst or to catch fire, may be produced in the battery cells.
FIG. 1 shows a basic circuit diagram of a traction battery 5 according to the prior art, such a traction battery 5 being known, for example, from laid-open patent application DE 10 2009 000 682. FIG. 1 shows two poles 10 and 20 which are electrically connected via a current path 30 on which battery cells 15, as voltage sources, are arranged in series, with the result that a voltage which is made available cumulatively by the cells 15 can be tapped via the poles. In addition, the module has a charging and disconnecting device 40 at the positive pole 10, a disconnecting device 50 at the negative pole 20 and a service plug 60.
FIG. 2 shows a basic circuit diagram of a battery cell 15 according to the prior art, such a battery cell 15 being known, for example, from U.S. Pat. No. 5,939,217. Said figure shows two poles 100 and 200 via which the voltage which is made available by means of the cell 15 can be tapped from a voltage source 300. In addition, the cell has a fuse 400 at the positive pole 100. The fuse 400 has the function of reliably disconnecting the voltage source 300 from the positive pole 100 in the case of an abnormal state of the temperature or current flow in the battery cell 15.
International Patent Application WO1993010589 discloses a device for balancing out the charge states of subunits of a battery. Each subunit is provided with a discharge circuit with resistors and fuses connected in series. The discharge circuit can be switched.